(1) Field of the Invention
The invention is related to a permanent magnet rotor with a shaft, a hollow cylindrical permanent magnet and an elastic connecting medium between the shaft and the permanent magnet, with the permanent magnet arranged coaxially around the shaft.
(2) Description of Related Art
A generic permanent magnet rotor is known from DE 23 28 886. In this design, a hollow cylindrical permanent magnet is mounted with the help of an elastic intermediate layer. The radial thickness of the elastic intermediate layer is measured in such a way that in case of sudden braking of the motor shaft, the permanent magnet can swing in the direction of the periphery, and thus prevent damage to the gear pinion. Other applications in which there are large temperature fluctuations, elastic intermediate layers help prevent mechanical tensions between materials subject to different degrees of heat expansion. However, it is this elastic intermediate layer that prevents a reliable permanent mechanical connection between the shaft and the permanent magnet. Another disadvantage is that the precision of the circular motion cannot be adequate in case of radial load, because the elastic material is of a yielding variety. Moreover, the material should not swell under the influence of humidity. Swelling could lead to the bursting of the permanent magnet.